Great Falls of the Potomac: When It Actually Flows
The Potomac drops over jagged ledges into Mather Gorge within sight of Washington, and the roar scales with everything that fell upstream in the last few days.
March through May
Big water window
in a typical year
Rain fed
What drives it
Potomac River
Live USGS
Data on this page
gauge 01646500
NPS Great Falls
Managed by
their rules govern
Trail status, closures and safety rules belong to each falls' managing agency, named and linked on every page.
The season
What fills Great Falls of the Potomac, and when
Great Falls is fed by the whole upper Potomac basin, so its volume tracks regional rain and snowmelt rather than any local creek. Spring runs highest. After a big upstream storm the falls can go from loud to frightening within a day, which is exactly what the downstream gauge shows before you leave home.
Typical best flow: March through May
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What the agency itself says
the Potomac River builds up speed and force as it falls over a series of steep, jagged rocks and flows through the narrow Mather Gorge
Source: USGS Water Services (National Water Information System). Instantaneous values and daily statistics services. U.S. Geological Survey data are works of the United States Government and are in the public domain. Gauge verified 2026-08-27.
Rain-fed falls carry the color of their watershed: Blackwater Falls runs amber with tannin from spruce and hemlock bogs upstream, and its volume tracks the last month of Appalachian weather. “Blackwater Falls (15437499241)” by Benjamin Smith from United States, CC BY 2.0
Getting there
Access, in the agency's words and ours
The Virginia side is Great Falls Park; overlooks are a short walk from the parking area. The Maryland side views the same drop from Olmsted Island.
Great Falls of the Potomac at moderate flow. The same ledges disappear under brown water after a big upstream storm. “Great Falls of the Potomac River in November, 2012” — National Park Service — Public domain
Common questions
Great Falls of the Potomac flow season FAQ
The reliable big-water window is March through May. Great Falls is fed by the whole upper Potomac basin, so its volume tracks regional rain and snowmelt rather than any local creek. Spring runs highest. After a big upstream storm the falls can go from loud to frightening within a day, which is exactly what the downstream gauge shows before you leave home.
This page reads the USGS gauge on Potomac River (POTOMAC RIVER NEAR WASH, DC LITTLE FALLS PUMP STA, downstream of the falls, the nearest long record on the main stem) live in your browser, and shows the latest flow next to the median USGS publishes for today's date, so you can see where today sits in the year. The gauge reads the river, not the brink, so treat it as the trend rather than a turnstile.
No. The Potomac is a major river and the falls run year round; the question here is how much, not whether.
Great Falls Park (National Park Service). The Virginia side is Great Falls Park; overlooks are a short walk from the parking area. The Maryland side views the same drop from Olmsted Island. Trail status, closures and safety rules are theirs, and their page is linked on this one; nothing here overrides what they publish.
In their own words: "Please remember that swimming and wading is prohibited in the Potomac River in Great Falls." That sentence is Great Falls Park (National Park Service)'s, quoted verbatim, and their page is the place to check before you go.
Yosemite Falls in May, running on snowmelt that will be gone by late summer. The National Park Service tells visitors the falls can be dry by August, which is why every falls page here starts from its watershed. “Tourists below Yosemite Falls (39832011431)” by Mike McBey, CC BY 2.0
Flow windows are typical-year climatology drawn from the driver and the agency language quoted above, not forecasts. Live readings and per-date percentiles are U.S. Geological Survey data, public domain; the above-or-below-typical line is our comparison and is labelled as such. Access, trail and safety information belongs to Great Falls Park (National Park Service). National picture: waterfall season across the US → Hero image: “Great Falls of the Potomac River in November, 2012” — National Park Service — Public domain
Places to stay